Oscillation generation



May 26, 1936.

N. E, LINDENBLAD OSC ILLATION- GENERATION Original Filed Oct. 4, 1950 5 Sheets-Sheet 1 lNV-ENTOR NILS BUNDENBLAD ATTORNEY y 1 N. E. LINDENBLADI 2,042,345

OSC'ILLATION GENERATION Original Filed Oct. 4', 1930 5 Sheets-Sheet 2 J2 WWWWWWWN ll l/ 74 INVENTOR NILS E. UNDENBLAD ATTORNEY y 1936. N. E. LIINDITINBLAD 2,042,345

050 ILLAT I ON GENERAT I ON ori inal Filed Oct. 4, 1930 s Sheets-Sheet 5 INVENTOR NILS E. uqoeuauxo ATTORNEY Patented May 26, 1936 UNITED STATES PATENT OFFICE OSCILLATION GENERATION Application October 4,

1930, Serial No. 486,375

Renewed October 25, 1934 21 Claims.

l '.'his invention appertains to the art of electrical oscillation generation and. especially to the production of ultra short wave length electrical oscillations. High frequency oscillations have been produced with an electron discharge device having an anode, a cathode and a grid or control electrode by applying positive potentials to the control electrode or grid relative to the potentials of the cathode and anode of the device. Of the electrons drawn towards the grid from the oathode, some miss their target (the grid) and pass through the grid structure. Immediately upon passing through the grid structure, the force from the positive grid potential has a braking or retarding effect upon the electrons instead of an accelerating force. Accordingly, the electrons are slowed down. If the anode be negative this will amplify the retarding or braking effect upon the electrons and they will finally stop, reverse, and be pulled towards the ,grid and eventually pass through the same in the opposite direction, approach the cathode, and, in the main, be stopped, reversed, and repeat the phenomenon described. The principle upon which oscillations are thus generated has generally been designated as the braking field or sometimes Barkhausen- Kurz principle. If the electrons stop exactly at the neutral region between the positive grid and the negative plate, they may there form a layer of electrons, which, as it assumes thickness, will explode, due to the repelling force between the electrons. Most of the electrons will, even in this case, return to the grid but some will eventually be pushed towards the plate. Moreover, it may also be said that the electrons, due to inertia, will not stop at the neutral point but continue past the same. In this case small variations in the plate potential will determine whether the electrons land on the plate or be returned before landing.

It should be understood, however, that at the present stage of the art there are several different opinions as to what actually takes place and no complete and fully acceptable theory is available.

Due to the inherently relatively large capacity of the electrodes of electron discharge devices used, it is not possible to produce oscillations in the manner described, beyond a certain limit in frequency. Accordingly, to reduce the effect of the high interelectrode capacity of the device thereby enabling production of ultra short wave length electrical oscillatory energy is the principal object of the present invention.

I have discovered, that by bringing a low loss, tuned circuit, or what I choose to term a catalyst element, more fully described hereinafter, in proximity to an oscillator of the type described, the element being preferably in the form of a conductor the equivalent in length of a multiple of a half wave length of a desired frequency of oscillation, high frequency oscillations, of a frequency heretofore impossible of production due to capacity effects within the tubes, can be produced.

I have further discovered that by placing the catalyst element too close or too far away from the oscillator may render the oscillator inoperative. Accordingly, a further object of my invention is to provide means for varying the coupling of the catalyst element or circuit and the oscillator.

Still a further object of my present invention is to provide a pushpull arrangement of oscillator of the type described and especially such an arrangement in combination with a catalyst element for the production of ultra short wave length electrical oscillations.

In accordance with United States Patent Office procedure, my invention is defined in the appended claims. However, it may best be understood both as to its structural organization and mode of operation by referring to the accom {panying drawings, which, it is to be clearly understood, are only illustrative of my invention, and wherein,

Figure 1 illustrates a simple form of my invention showing a catalyst element in proximity to a high frequency electron discharge device oscillator,

Figure 2 illustrates a pushpull oscillator utilizing a catalyst element for starting and maintaining high frequency electrical oscillations,

Figure 3 diagrammatically illustrates a simplified modification thereof,

Figures 4, 5, and 5a. illustrate catalyst elements together with means for varying the tuning thereof as well as coupling thereof to an oscillator, and

Figure 6 illustrates apparatus for universally mounting the catalyst element.

Turning to Figure 1 of the drawings, as indicated, negative potentials may be applied to anode 4 and the cathode 2 which, however, is preferably left at zero potential, of an electron discharge device 6 whose grid or intermediate control element 8 is maintained at a relatively positive potential. The anode 4 may be, if desired, an electron emitting electrode similar or ,means of a transmission line I0, coupled to a suitable radiator [2.

By virtue of the high velocities imparted to electrons emanating from the cathode by the action of the positive potential on grid 8, some of the electrons from the cathode will pass through the grid instead of bombarding the same, and approach the anode 4, at which time the electrons are slowed up. The electrons are then in the main reversed by the combined action of the positive potential on the grid and negative charge on the plate and given a new motion towards the grid with a repetition of the phenomena previously described; i. e., some will bombard the grid and some will continue through it towards the cathode when the oscillatory action so far described is again repeated. There may, however, be additional phenomena taking place due to space charges, but there is no satisfactory theory available at the present time to completely take care, of this condition. 7

However, although the frequency of oscillations generated in this manner is relatively high, there is an upper limit set by the interelectrode capacity. As the reactance of this capacity becomes lower and lower the higher the frequency becomes, the short circuiting effect of this reactance becomes greater and greater preventing voltage variations from taking place on the electrodes. From experience it seems necessary that such variations take place in order that oscillations be maintained, or, in other words the electrons themselves are not the sole. performers in producing these oscillations. Even at very low interelectrode capacitive reactance, the voltages may be varied if enough circulating current is available which, of course, is a matter of efliciency in the oscillating circuits. This is chiefly the function of the hereinafter catalyst circuit referred to, and to be more fully described.

By coupling a catalyst element l4 to the electrodes of electron discharge device 6, either within or without the device 6, and preferably outside of the envelope of the electron discharge device, the catalyst element l4 preferably in the form of an open tuned circuit such as a half wave length conductor, or, for structural convenience, an odd multiple of a half wave length long, will take energy from the device and feed it back in a fashion such as to assist in the starting and maintaining of ultra short wave length energy. That is, I have. discovered that an open tuned circuit, such as described, when brought into the vicinity of the tube brings high frequency life into it when suitable voltages are applied to the electrodes of the tube and the tube circuits such as radiator l2 are properly tuned at the working frequency.

I have further discovered that bringing catalyst circuit or conductor M in the formof a metallic strip usually of copper or of a section of a copper sheet, is brought too close to the tube elements, or moved too far therefrom, the tube will cease operating at the high frequency. Therefore, a prerequisite to proper action of the catalyst element is that it is capacitively coupled to stray fields from the electrodes of the device and especially the anode of the oscillator. And, although the catalyst circuit obtains energy from the very circuit to which it is rendering assistance, I have found that with proper spacing and adjustment as indicated, action of the element is very positive and oscillation generation is self starting.

I have used my invention with success in connection with a pushpull oscillator, I have devised, utilizing electron discharge devices operated in the fashion described in connection with Figure 1. A pushpull operating system according to my invention, is shown diagrammatically in Figure 2 wherein the cathodes of electron discharge devices l6, H! are made preferably of the heater type and supplied with heating energy from suitable transformers 2D, 22. The grids of the devices are connected together through a single loop conductor 24 and supplied as shown at the mid point of the conductor 24 with positive potential. The anodes are similarly connected together by a conductor 26 supplied at the center of the loop portion 28 with potential from a suitable potentiometer 30, together with modulating potentials applied through a transmitter 32 amplifier 34 and coupling transformer 36. Output energy is taken from a transmission line 38 coupled to the loop portion 28 of conductor 26 and fed to a suitable I utilization circuit here shown in the form of a half wave length radiator 40. In order to vary the output circuit coupling, loop 29, coupled to loop 28, is oscillatably mounted upon an insulating block 3|. The block, and hence the coil or loop 29, may be rotated relative to loop 28 through action of knob 33 and shaft 35.

. To start and maintain oscillations of ultra short wave lengths, a catalyst element in the form of a half wave length U-shaped strip 42 conveniently of copper, or if desired, any other metal or conducting composition, is provided. The terminal pieces 44 of the strip face the exterior portions of tubes l6, l8 and by capacitive coupling of the impedance of the catalyst to the tube elements,

the effective capacity of the latter is reduced,

because the catalyst circuit carries the greater portion of the circulating current necessary to swing the voltage of the tube elements, thus relieving the ordinary leads that go through the glass from this duty. The catalyst circuit can carry this heavy current at a low loss of energy whereas the ordinary tube leads oifer a loss which prohibits oscillations from taking place.

By means of a screw threaded rod 46 rotatably keyed at 48 to the trough-a voltage nodal point--of U-shaped catalyst element 42 and screw threaded in a suitable support 50, the distance of the feet or terminals from the tubes may be Varied, thereby adjusting coupling of the catalyst element to the tubes.

If desired, of course, as shown in Figure 3, the catalyst may simply be in the form of a straight copper strip or shield 52 placed in close proximity to the tubes such that the stray capacitive fields about the tube link with the catalyst element as illustrated.

To provide for fine variation in coupling of the catalyst element with the tubes, the arrangements shown in Figures 4 and 5 may be utilized to good advantage. In Figure 4 the'catalyst element is in the form of a trombone slide, having an independently adjustable trough-like portion 54 and independently adjustable feet 56, 58 which may be independently adjusted by screw threaded rods 60, 62 rotatably keyed to the feet and screw threaded within a suitable support 64. Suitable insulators GI, 63 are placed in the rods 60, 62. The slide 54 may contain an internally screw threaded member 66, to which rod 68 is screw threaded. The rod 68 is rotatably keyed to support 64 at point 10' as shown.

While the arrangement shown in Figure 4 allows of adjustment of the catalyst element to-,

Wards and away from the oscillators, by mounting Oil support 64 as shown in Figure 6, angular adjust- 'low loss tuned circuit and reapplying the energy ment is also possible.

Thus, by means of gears 12 and screw 14, the entire catalyst element of Figure 4 may be rotated in one plane, and by means of another gear and screw arrangement 16, the catalyst may be turned in another plane perpendicular to the first plane.

Another preferred form of catalyst structure is shown in Figures 5 and 5a whereinthe terminals or feet of the catalyst element comprise two pieces 5|, 53, slidable over terminals 55, 51 and retained in desired position by bolts 59.. In this manner, the area of the terminals coupled to the tubes l6,

l8 can be varied as desired.

The sections or legs 6| may be supported by legs 63, adjustably mounted on insulating member 65 by means of a suitable slot and bolt arrangement 1|. 7

Movement of screw threaded rod 13 for varying the overlapping of the trough 15 and the legs 6| may be accomplished by a. crank 11 as shown. The rod, of course, is rotatably mounted but axially fixed in support 19.

It is to be understood, of course, that the catalyst element described in connection with Figures 2, 4, 5, and 6, may also be used in connection with a single tube rather than a pair of pushpuil connected devices. In addition, although energy may be taken from the catalyst circuit, it is preferred to have an independent output circuit for the oscillator and leave the catalyst free solelyfor the starting and maintaining of high frequency electrical oscillations.

- Output energy may be taken from any pair. of electrodes, and, in the case of a single tube may be taken from any two dissimilar electrodes. Modulation may not only be accomplished by variation in grid voltage, but it may also be accomplished by variation in anode voltage as well; for, I have found, pure amplitude modulation may be obtained by varying grid and anode voltages simultaneously. For a more complete description of the latter feature see my United States Patent No. 1,938,749, granted December 12, 1933.

Having thus described my invention, what I claim is:

1. In a braking field type of electron discharge device oscillator having, in combination therewith, a low loss circuit externally coupled thereto, the method of starting and maintaining oscillations in said electron discharge device oscillator which includes capacitively by-passing high cur rent, high frequency energy from the oscillator into said low loss circuit and applyingthe energy in the low loss circuit to the oscillator.

2. In an electron discharge device oscillator having a control electrode intermediate other electrodes and maintained at a positive potential relative to the potential of the other electrodes and a low loss circuit capacitively coupled to said electrodes, the method of starting and maintaining oscillations with the oscillator which includes transferring energy from the oscillator into said low loss by-pass circuit.

3. In a braking field type of electron discharge device oscillator having a control electrode intermediate other electrodes and maintained at a positive potential relative to the potential of the other electrodes in combination with an external low loss tuned circuit capacitively coupled to the electrodes of said oscillator, the method of starting and maintaining oscillations with the oscillator which includes transferring energy from the oscillator to the external, capacitively coupled,

in the circuit to the oscillator electrodes.

4. In combination, a braking field type of electron discharge device oscillator and an external circuit in close proximity and capacitively coupled thereto for starting and maintaining oscillations.

5. In combination, a braking field type of electron discharge device oscillator, an external conductive element physically separated from said device, adjacent and coupled thereto, and means for varying the coupling between the element and the device.

6.'In' combination, an electron discharge device oscillator, an external open tuned circuit physically separated therefrom in close proximity thereto for starting and maintaining oscillations, and, an output circuit independent of the open tuned circuit, fed by the oscillator.

'7. In combination, an electron discharge device oscillator having a plurality of electrodes, a conductor the equivalent of an odd multiple of a half wave conductor physically separated from said electrodes and in close proximity thereto for starting and maintaining oscillations, and, an output circuit, independent of the conductor, fed by the oscillator.

8. The combination of an electron discharge device having a plurality of electrodes one of which is intermediate other of the electrodes and a source of potential for maintaining said one electrode at a positive potential relative thereto, a conductor the equivalent of an odd multiple of a half wave conductor, physically separated from said electrodes, adjacent the oscillator and coupled thereto, means for varying the distance between the conductor and the oscillator, and, an output circuit independent of the conductor, coupled to the oscillator.

9. The combination as claimed in claim 8 wherein the conductor is in the form of .a U- shaped strip having feet adjacent the devices.

10. An oscillator circuit having,. in combination, two electron discharge devices in .pushpull relationship, each of said devices comprising an evacuated container within which are located anode, cathode and. control electrodes, means for maintaining the control electrode of each device at a positive potential with respect to the other electrodes of the same device, a circuit connection having uniformly distributed inductance and capacity connecting together the control electrodes of said two electron discharge devices, and an additional circuit having uniformly distributed inductance and capacity, said additional circuit being solely capacitively cou-' pled to corresponding electrode elements of said devices.

11. An oscillator circuit having, in combination, two electron discharge devices in push-pull relationship, each of said'devices comprising an evacuated container within which are located anode, cathode and control electrodes, means for maintaining the control electrode of each device at a positive potential with respect to the other electrodes of the same device, a circuit connection having uniformly distributed inductance and capacity connecting together the anode electrodes, and an additional circuit having uniform- 1y distributed inductance and capacity, said additional circuit being solely capacitively coupled to corresponding electrode elements of said devices.

12. An oscillator circuit having, in combination, two electron discharge devices in push-p111] relationship, each of said devices comprising an evacuated container Within which are located anode, cathode and control electrodes, means for maintaining the control electrode of each device at a positive potential with respect to the other electrodes of the same device, a first circuit connection having uniformly distributed inductance and capacity connecting together the control electrodes of said two electron discharge devices, a second circuit connection having uniformly'distributed inductance and capacity connecting together the anode electrodes of said devices, and an additional circuit having uniformly distributed inductance and capacity, said additional circuit being capacitively coupled to corresponding electrode elements of said devices.

13. A pair of electron discharge devices connected in push-pull with respect to one another, each device having an electrode intermediate other electrodes, a source of potential for maintaining said intermediate electrode of each device at a positive potential with respect to the other electrodes of the same device, and a low loss circuit external of said devices and capacitively coupled to the electrodes thereof for starting and maintaining high frequency oscillations.

14. A pair of electron discharge devices connected in push-pull relation with respect to one another, each device having an electrode inter mediate other electrodes, a source of potential for maintaining said intermediate electrode of each device at a positive potential with respect to the other electrodes of the same device, and a catalyst element in the form of a conductor the equivalent of a multiple of half the operating wave length capacitively coupling the electrodes of said two devices together for starting and maintaining electrical oscillations.

15. A circuit as defined in claim 14 characterized in this, that said catalyst element is U- shaped and has feet extending outward from the extremities thereof and adjacent the devices.

16. A circuit as defined in claim 14 characterized in this, that said catalyst element is electrostatically coupled to'said devices for starting and maintaining oscillations, and means are pro vided for adjusting the coupling of the catalyst element to said devices.

17. An oscillator circuit having, in combination, two electron discharge devices in push-pull relationship, each of said devices comprising an evacuated container within which are located anode, cathode and control electrodes, a source of potential for maintaining the control electrode of each of said devices at a positive potential relative to the anode and cathode of the same device, a first circuit connection having uniform- 1y distributed inductance and capacity connecting together the control electrodes of said two electron discharge devices, a second circuit connection having uniformly distributed inductance and capacity connecting together the anode of said devices, and an additional circuit having uniformly distributed inductance and capacity, said additional circuit being external of said devices and electrostatically coupled to corresponding electrodes of said devices.

18. In combination,'a braking field type of electron discharge device oscillator and an external circuit in close proximity and capacitively coupled thereto for starting and maintaining oscillations, said circuit comprising a conductor whose electrical length is equivalent to an odd multiple of half the length of the operating wave.

19. An electron discharge device oscillator having, within an envelope, an anode, cathode, and an electrode between said anode and cathode, a source of potential for maintaining said electrode between said anode and cathode at a positive potential relative to said anode and cathode, a circuit whose electrical length is equivalent to an odd multiple of half the length of the operating wave external of said envelope, physically separated from said electrodes, and coupled thereto.

20. An oscillation generation circuit comprising a pair of electron discharge devices connected in push-pull relationship with respect to one another, each of said devices comprising an evacuated container within which are located anode, cathode, and control electrodes, a circuit devoid of concentrated reactance connected between the control electrodes of said devices and another circuit devoid of concentrated reactance connected between the anode electrodes of said devices, said cathodes of said devices being connected together, a source of potential for subjecting the control electrodes of each device to a suitable potential with respect to the other electrodes of the same devices, and a low loss con ductor a multiple of a one-half Wave length long coupling like electrodes of said two devices together for maintaining electrical oscillation generation by said devices.

21. An oscillation generation circuit comprising a pair of electron discharge devices connected in push-pull relationship with respect to one another, each of said devices comprising an evacuated container within which are located anode, cathode, and control electrodes, a tuned high frequency circuit devoid of concentrated reactance connected between the control electrodes of said devices and another tuned high frequency circuit devoid of concentrated reactance connected between the anode electrodes of said devices, said cathodes of said devices being connected together, a source of potential for subjecting the control electrodes of each device to a suitable potential with respect to the other electrodes of the same devices, and a low loss tuned conductor a multiple of a one-half wave length long coupling like electrodes of said twodevices together for maintaining electrical oscillation generation by said devices.

' NILS E. LINDENBLAD. 

